This invention relates to the eradication and control of insects in building structures by fumigation with insecticidal gases. One of the common methods of treating building structures is to enclose the building structure in a vapor barrier, either built in to the structure or added to the structure, or a combination of the above, and fill the barrier with a gas which kills the insects in the building structure. The technique is particularly applicable to small- and medium-sized buildings which are reasonably susceptible to being "tented," i.e., having a tent built over and about the building structure for containing the insecticidal gas. Similar techniques may be used in treating animal shelters as well as dwelling houses and business buildings designed for human occupancy.
A number of gases are known to be suitable for fumigation of building structures to eradicate insect infestations in the structures. Methyl bromide, for example, is a widely used fumigant. The method, conventionally, requires that the building structure be enclosed in a substantially gas-impermeable barrier. Depending upon the building structure, this may comprise tenting the entire building above the ground surface by covering it with a polymer or fabric-reinforced polymer tent, which may be one piece or may be made up of several pieces which are clipped or bound together to form a substantially gas-impermeable seam. It is common practice, for example, to provide seams between large tarpaulins of polymer membrane or fabric-reinforced polymer membrane by rolling the edges of the tarpaulins together and securing the rolled portions by clips spaced at sufficient intervals to maintain the rolled seam. For smaller structures, a single-piece tent may suffice, but for larger structures, a multiple-piece tent is usually required. Once the structure is tented and the tent is secured to the ground or the surrounding supporting surface by clips, weights, tape or other means, an insecticidal gas is introduced into the tent. This may be done by a hose which enters into the tent by, for example, pumping the insecticidal gas from a service truck outside the building. The gas may also be introduced by a "bomb" or "charge" of insecticide inside the building which may be set off by a timer or by an external signal, such as a radio frequency-controlled signal, for example. Depending upon the relative density of the gas which serves as the insecticide as compared with air, vents may be provided at the top of the tent or near the bottom to permit the air to escape as the insecticidal gas fills the tent. Once the tent is filled with insecticidal gas, the building is maintained in its tented condition for a suitable period of time, usually several hours, to permit the gas to permeate into all of the spaces in the building, including small pours in the wood structures, borings of insects into the wood, etc., so that the insecticide reaches all of the insects, larvae, and eggs of the insects. Depending upon the insecticide, the insects may be totally destroyed, in all stages of their life cycle, or it may be necessary to repeat the fumigation periodically as new life cycles occur.
Methyl bromide is given as a typical example of the kind of insecticidal gas which may be used in connection with this invention and which is used in the conventional fumigation practice. Other insecticides may be used, such as 2-methyl-4-oxo-3-(2 bropynyl)cyclopent-2-enyl chrysanthemate, formaldehyde (usually for animal shelters and not for human shelters), which may be generated from paraformaldehyde flakes or formalgen, or any other insecticide, since the nature of the insecticide is not critical insofar as the present invention is concerned. The foregoing is all prior art, and constitutes the prior art as to which the present invention is an improvement.
It is immediately apparent from a careful consideration of this well-known practice, and is well understood and recognized in the art, that there are two major disadvantages of this technique. First of all is the ecological impact of introducing insecticidal gas into the atmosphere. Regardless of the recovery techniques utilized, if any, it is inevitable that substantial amounts of the insecticidal gas will escape into the atmosphere. In most operations, no effort is made to recover the insecticide from within the tent, and the entire volume of insecticide is simply permitted to escape into the atmosphere. While most of these insecticides are not highly toxic to humans, all of them inherently have a certain level of toxicity. The addition of these toxic gases to the atmosphere, particularly in areas where the atmosphere tends to become somewhat stagnant, such as in the Los Angeles basin of Southern California, in London, and in certain other areas, the addition of toxic gases to an already pollutant-laden atmosphere becomes a very serious consideration. While some of these insecticidal gases hydrolyze and become less toxic, or otherwise react with components of the atmosphere and become less toxic, generally speaking these pollutants remain in their toxic state in the atmosphere for long periods of time, the only dissipating force being the simple dilution in the atmosphere. Over a long period of time, of course, most organic compounds will be broken down, but this may take months or even years, and some such compounds are extremely stable over very long periods of time. It would, therefore, be a very great step forward in the art to reduce the amount of insecticidal gas pollution resulting from building structure fumigation.
The other major consideration is the cost of the insecticidal gas. It will be readily understood that it is necessary to completely fill the building structure with the insecticidal gas, even though much of the structure itself is simply open space or substantially open space. If it were possible to obtain the same concentration of insecticidal gas in and around the buildings structures per se, without supplying sufficient insecticidal gas to fill the entire building structure, it would be a very great step forward in the economics of fumigation.
It is to the foregoing problem that the present invention is addressed.
The present invention is an improvement in the fumigation of a building structure which is normally enclosed in a substantially gas-impermeable barrier by the introduction of an insect-eradicating gas, the improvement being inflating an expandable bladder in substantially open spaces in the building before the introduction of the insect eradicating gas.
As an overall process, the invention may be described as the steps of placing one or more expandable bladders inside the building in one or more substantially open spaces which are defined by the building structure, or by the contents of the building, then inflating the bladder with inert gas, e.g. air, to cause the bladder substantially to fill and to occupy the substantially open space at the building, thereafter enclosing the building structure and carrying out the fumigation in the usual manner, while maintaining the bladder in its inflated condition to occupy the substantially open space of the building. After the fumigation is completed, the insect-eradicating gas is removed from the building, the building is opened, and the bladder is deflated and removed.
Depending upon the size, construction and usage of a particular building, it is possible, using the present invention, to reduce the effective volume of the building by from 50% to 80% and, thereby, reduce the insecticidal gas by approximately the same percentage.